Foam, having electrically conductive properties, is desirable for use in environments where electronic components or discrete devices may be subject to a static charge, either generated by people or the environment, itself, such as in shipping, transporting, or otherwise moving such electronic components from place to place, both in manufacture of electronic devices and equipment and in transporting both discrete devices and equipment. Typically, in an electronic manufacturing operation, production personnel utilize inexpensive synthetic materials for floor covering, as well as wearing apparel, such material being subject to rapid static-charge buildup and maintenance. Likewise, in shipping electronic components and devices, the shipping-room and receiving-room personnel may generate static charges in a normal course of business, which may be imparted to electronic components or devices in their handling and shipping.
It has been an accepted occurrence that some metal-oxide semiconductor (MOS) devices can be destroyed by less than 100 volts of static charge, and field-effect transitors (FET) are also damaged by static charges. Personnel handling such devices can easily hold over 10,000 volts of static charge. MOS manufacturers often utilize equipment and safeguard systems to prevent static-charge accumulation and subsequent destruction of these electronic devices. MOS devices are often packaged in conductive materials, spring clip and conductive dual in-line sticks. These forms of packaging short or shunt the devices, so that all have the same potential. Some manufacturers ship their devices with conductive leads shorted with a wire spring clip or aluminum dip stick. Such protection is also sought for MOS/FET circuits, as well as microprocessor chips and various integrated circuits.
In these environments, conductive products are utilized in order to provide a circuit to ground for any static electrical charge which has been built up or to provide a means to short all the leads on an electronic component to prevent a potential difference between such leads. Conductive bags made of polyolefin and conductive foam made of polyurethane have been used in the past in these environments to alleviate the static electrical problem. The conductive foam may be of different thicknesses and of either low or high density. The low-density foam is very soft and provides a cushion to prevent damage to devices in their transport. High-density foam provides a crisp surface into which discrete components may be inserted directly to provide a circuit to ground, as well as to short the lead to prevent a potential difference across the discrete component.
Therefore, it is desirable to provide an improved conductive foam adapted for use in such environment, and particularly to provide an improved, economical, easily manufactured conductive foam for use in the electronics-manufacturing facility, as well as in shipping electronic devices.